Frequency of Occurrence of Letters in English

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Frequency of Occurrence of Letters in English

The following table and text are from:
Fletcher Pratt, Secret and Urgent: the Story of Codes and Ciphers Blue Ribbon Books, 1939, p. 252.

Rank	Letter	Frequency of occurrence in 1000 words	Frequency of occurrence in 1000 letters
1	E	591	131.05
2	T	473	104.68
3	A	368	81.51
4	O	360	79.95
5	N	320	70.98
6	R	308	68.32
7	I	286	63.45
8	S	275	61.01
9	H	237	52.59
10	D	171	37.88
11	L	153	33.89
12	F	132	29.24
13	C	124	27.58
14	M	114	25.36
15	U	111	24.59
16	G	90	19.94
17	Y	89	19.82
18	P	89	19.82
19	W	68	15.39
20	B	65	14.40
21	V	41	9.19
22	K	19	4.20
23	X	7	1.66
24	J	6	1.32
25	Q	5	1.21
26	Z	3	.77

"The average length of English words is 4.5 letters per word.

It will be noted that the letters, when arranged by relative frequency, fall into certain well-defined groups.

In short messages, and in all text where there are less than 1500 words, any letter in one of these groups may show a higher frequency than another letter of the group though in text consisting of more than 200 words a letter rarely shows such frequency or infrequency as to fall in the wrong group.

For convenience' sake the groups may be listed as follows:

I	E
II	T
III	A, O, N, R, I, S
IV	H
V	D, L, F, C, M, U
VI	G, Y, P, W, B
VII	V, K, X, J, Q, Z

If the word "the" is omitted from a given cipher message, T drops into the third group and H into the fifth."

Verified by: DT 3/99

Disclaimer:
While the Library has verified the information presented in these files in what it considers to be reliable and authoritative sources, it cannot take responsibility for nor guarantee the accuracy of the information presented.